console.log("-".repeat(10) + "例1" + "-".repeat(10));
const keys1 = Object.keys({
  name: 'empty',
  age: 0
});
console.log(keys1);
/*
  [ "name", "age" ]
*/
console.log("-".repeat(10) + "例2" + "-".repeat(10));
const obj1 = {
  name: 'zg',
  age: 18,
  friends: ["lucy"],
};
const keys2 = Object.keys(obj1);
console.log(keys2);
/*
  [ "name", "age", "friends" ]
*/
